Multilayer surface-mount 3dB directional coupler for application in balanced modulators

A 3-dB coupled-line surface-mount directional coupler has been designed. As a base substrate a common FR4 laminate has been used. Three-strip coupled-line configuration of the coupled lines has been chosen in order to achieve good return loses and high isolation of the designed coupler. The designed coupler has been used in the development of balanced modulators. Measurement results of the designed directional coupler and modulators are shown.